Method for killing plants



a number of different points so that a Patented June 19, 1945 2,378,716 METHOD FOR/KILLING PLANTS George E. Lynn and Bernard J.- Thlegs, Midland,

Mich, assignors to The Dow Chemical C ompany, Midland, Mich, a corporation of M1chi-- gan No Drawing. Application March 2, 19M,

- Serial No. 524,808

3 Claims.

This invention relates to a method for killing plants, and is particularly concerned with the control of weeds and other undesirable vegetation by the application of phytocidal agents thereto.

Many organic and inorganic compositions have been suggested for use as herbicides and for retarding or otherwise regulating plant growth.

Commonly accepted materials for the killing of weeds or control of other undesirable vegetation are "the inorganic chlorates, the salts of dinitrophenols, and petroleum oil. The chlorates and dinitrophenolates are disadvantageous fdr use by reason of the highly flammable nature of deposits thereof on the dead and dried plant residues. Also, each is objectionable from the point of view of the operator, since residues on clothing are so flammable as to constitute a serious hazard. Furthermore, aqueous solutions of the chlorates are very corrosive to metal containers and applicators, whereby specialized equipment is required for theirhandling.

Similar disadvantages accrue to the conventional use of heavy petroleum oils. Here the oily non-volatile residues remaining on the vegetation constitute a fire hazard, and those portions of the treating material deposited in and on the soil may interfere with its subsequent utilization for long periods of time. Also, it has been found that oil has little eiiect upon the root systems of weeds and shrubs, whereby a temporary control may be followed by the growth of suckers or the resprouting of the unaffected roots.

Among the noxious plants which have proven very difllcult to control by the usual methods is bindweed. The problem here is to accomplish the killing of-the plant root system which may up of the leaves and stalk of bindweed, the roots mixture asherein employed, refers to composidiscovered that plants, and more particularly weeds and other obnoxious vegetable growth, can

be killed by applying to the leaves and stalks of' such plants and to the soil adjacent thereto a liquid dichloro-nitro-benzene mixture. The proper and timely application of such herbicidal mixture results in the killing of the treated plant and the control of borers, nematodes, and other organisms present'in and on the treated plant or in the soil adjacent theretoand which may be contacted with either the liquid toxicant or vapors thereof. Deposits of the herbicide in or on the soil gradually volatilize and exert a blanketing effect, penetrating to the depth of several'inches. This results in the destruction of the root system to a considerable distance fromthe crown of the treated plant and the killing over a period of at least one growing season of new shoots and suckers which may develop. The dichloro-nitrobenzenes are not readily flammable nor explosive and are sufilciently volatile as to be dispersed from the soil after a reasonable period and not to leave objectionable residues either in the soil 'or on dried cellulosic plant structures.

The expression liquid dichloro-nitro-benzene tions consisting of two or more of the isomeric dichloro-nitro-benzenes in such proportion as to be liquid at ordinary temperatures. As constituents of such mixture, 2.4-dichloro-nitro-benzene, 2.5-dichloro-nitro-benzene, 2.6-dichloronitro-benzene, 3.4-dichloro-mtro-benzene, and 2.3-dichloro-nitro-benzene are satisfactory.

When operating in accordancewith the invention, the liquid dichloro-nitro-bemene mixture may be employed without modification. In a further embodiment such mixture may be employed not infrequently send up new sprouts at one, or"

permanent control is not obtained.

It is among the objects of 'the present invention to provide an improved procedure for killing plants by the application of phytocidal agents ,,,.thereto. Another object is to provide a plant in aqueous emulsion or dissolved in a more volatile organic solvent. An alternate procedure comprises employing the dichloro-nitro-benzene mixturedispersed in or on a finely-divided solid such as wood flour, talc, diatomaceous earth, bentom'te,

pyrophyllite, clay, etc.

The amount of dichloro-nitro-benzene mixture employed varies with the form of the composition, the time in the growing season in which treatment is to be made, and the variety and age of plant to be treated. For the control of grass object is to provide a specinc'method for the control of bindweed. Other objects will become or weeds, any required amount of the material may be sprayed, poured, or dusted over the area on which it is desired to obtain the herbicidal efiect. Also spot applications may be made to individual plants or plant clumps.

In carrying outthe invention, the liquid dichloro-nitr'o-benzene may be applied to the plants at any time during the growing season. An optimum effect upon leaves, branches, stalks, and

roots is obtained when the composition is applied in the spring or early summer. Following application of the herbicide to the plant surfaces and soil, there is a withering and shrinking of the foliage and stem portions of the plant. The root Example 1 Mature bindweed plants growing on a heavy clay soil were subjected to spot treatment with a liquid dichloro-nitro-benzene mixture containing 58 per cent by weight of 3.4-dichlor'o-nitrobenzene, 37 per cent of 2.3-dichloro-nitro-benzene, and per cent of closely related dichloronitro-benzene products. In this operation, a 5 milliliter portion of the herbicide mixture was poured onto the crown of each plant. This application was made during the late spring. One month thereafter all of the aerial portions or the treated plants were dead, and excavationof the roots showed them to have been destroyed to a depth of about 5 inches below the soil.

Example 2 bindweed plants, it was found that new shoots had started in many places only to be killed at approximately 3 to 4 inches below the soil surface by the blanket of dichloro-nitro-benzene fumes.

. Example 3 90 parts by weight tr the dichlor'o-nitro-benstirring this product with water in the proportion of 1.5 pounds of concentrate per gallon of water. 30 gallons of this spray, containing about 45 pounds of the dichloro-nitro-benzene mixture,

- the roots of which are contacted with lethal conwas applied with a power sprayer to 1000 sq. feet of a mixed stand of bindweed and field grasses. This application was made in mid-summer. The

vfollowing day all treated foliage and blossoms were wilted down. It was found that the treatrnent accomplished substantially complete control, of plant growth over the balance of the growing season. s.

Example 4 30 pounds of a liquid mixture of isomeric dichloro-mononitro-benzene is mixed with 100 pounds of fine sawdust and the resulting product scattered broadside over a mixed weed stand containing ragweed, pigweed, and plantain. This treatment is adapted quickly to kill those plants whose foliage is contacted with the composition, and to cause the eventual destruction of all plants,

centrations of dichloro-mononitro benzene vapor as the latter penetrates the soil.

We claim:

1. A. method for killing plants which includes the step of applying to and about the growing plant an herbicide including as a principal toxic ingredient a liquid dichloro-nitro-ben'zene mixture. o

2. A method ior killing weeds which comprises spraying the ground adjacent to the weeds and the weed tops with a composition including a liquid dichloro-nitro-benzene mixture as a printhe ground adjacent thereto a liquid dichlorointro-benzene mixture.

GEORGE E. LYNN. BERNARD J. THEGS- 

